<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <form id="submit" action="">
        <p><input type="text" id="user"></p>
        <input type="submit">
    </form>
    <script>
        var submit = document.getElementById("submit");
        var user = document.getElementById("user");
        submit.onsubmit = function(event){
            if(user.value=="abcd"){
                window.location.href = "https://www.baidu.com";
            }
            // event.preventDefault();
        }

        
    </script>
</body>
</html>